The most basic chemical question confronted by these studies is "How can metal ions influence chemical reactions?" Interest continues on the stereochemical control of chemical reactions by metal ions, as illustrated by use of the coordination template effects in ligand synthesis. These studies underlie the synthesis of a broad range of complexes of macrocyclic ligands that may serve as analogs to such natural macrocyclic complexes as the porphyrins and vitamin B12. We are seeking to learn those chemical principles that are either unique to macrocyclic ligand structures or are maximized or minimized by such structures. The complexes of iron are of special interest because of their importance in heme proteins. Properties and reactions of interest in exploring the chemistry of these macrocyclic complexes are electrode potentials and kinetics, stabilization of extreme oxidation states, ability to catalyze peroxide decomposition, and oxidation of substrates, the formation of O2 complexes and the formation of metal-carbon sigma bonds.